Compressor

ABSTRACT

A compressor includes fixed and movable side members. The fixed side member has a discharge port opened/closed by adischarge port. The discharge valve has a valve body which closes/opens an outlet end of the discharge port. An area of an inlet end of the discharge port is Ai, a peripheral length of the inlet end is Li, and a hydraulic diameter Di of the inlet end is 4(Ai/Li). A peripheral length of the outlet end of the discharge port is Lo, a reference lift amount of the valve body is ho, a cross sectional area Ao of an outlet side flow path formed between the outlet end of the discharge port and the valve body is Lo×ho, and a hydraulic diameter Do of the outlet side flow path is 4(Ao/2Lo). A ratio (Do/Di) is 0.25 or more and 0.5 or less.

TECHNICAL FIELD

The present invention relates to compressors having a discharge valve.

BACKGROUND ART

Compressor having a discharge valve for opening/closing a discharge porthave been known. For example, Patent Document 1 discloses a rotarycompressor which has a so-called reed valve as a discharge valve. PatentDocument 2 also discloses a discharge valve similar to the dischargevalve in Patent Document 1.

In the rotary compressor of Patent Document 1, the discharge valve isprovided at a main bearing. The discharge valve has a plate-like valvebody provided so as to cover an outlet end of a discharge port. In thestate in which the internal pressure of the compression chamber is lowerthan the back pressure of the valve body, the valve body closes thedischarge port and prevents a hack-flow of a fluid into the compressionchamber. On the other hand, in the state in which the internal pressureof the compression chamber is higher than the back pressure of the valvebody, the valve body is elastically deformed and is separated from theoutlet end of the discharge port. Thus, the high-pressure fluid in thecompression chamber passes through the outlet end of the discharge portand the valve body, and flows out.

CITATION LIST Patent Document

Patent Document 1: Japanese Unexamined Patent Publication No.2008-101503

Patent Document 2: Japanese Unexamined Patent Publication No.2002-070768

SUMMARY OF THE INVENTION Technical Problem

To improve the efficiency of the compressor, it is preferable to reduceas much pressure loss as possible at a time when the fluid flows outfrom the discharge port, and it has been thought until recently that inorder to reduce the pressure loss at the time when a fluid flows outfrom a discharge port, it is preferable to increase a gap between thelifted valve body and the outlet end of the discharge port as much aspossible, and to do so, that it is necessary to increase a lift amountof the valve body of the discharge valve as much as possible.

On the contrary, the inventors of the present application found thatonce the lift amount of the valve body of the discharge valve exceeds apredetermined degree, the pressure loss at the time when a fluid flowsout from the discharge port is not much reduced even if the lift amountis further increased. The reason why this happens is as follows. As willbe explained in detail later, the greater the lift amount of the valvebody of the discharge valve is, the larger a vortex formed around theoutlet end of the discharge port becomes. The vortex interrupts a flowof the fluid passing through the gap between the outlet end of thedischarge port and the valve body. Thus, once the lift amount of thevalve body of the discharge valve reaches and exceeds a predetermineddegree, the pressure loss at the time when a fluid flows out from thedischarge port is not much reduced even if the lift amount of the valvebody is further increased, because of an increase in the effects of thevortex.

The present invention is thus intended to improve the efficiency of acompressor by appropriately setting a lift amount of a valve body of adischarge valve.

Solution to the Problem

The first aspect of the present invention is directed to a compressorhaving a fixed side member (45) which forms a compression chamber (36)and a movable side member (38) which is rotated and changes a volume ofthe compression chamber (36), the compressor configured to suck a fluidinto the compression chamber (36) and compress the fluid. The fixed sidemember (45) is provided with a discharge port (50) that penetrates thefixed side member (45) and leads the fluid out of the compressionchamber (36), and a discharge valve (60) that opens/closes the dischargeport (50), the discharge valve (60) has a valve body (61) which closesthe discharge port (50) by covering an outlet end (52) of the dischargeport (50) and opens the discharge port (50) by being lifted from theoutlet end (52) of the discharge port (50), an area of an inlet end (51)of the discharge port (50) is Ai; a peripheral length of the inlet end(51) is Li; and a hydraulic diameter of the inlet end (51) is defined byDi=4(Ai/Li), a peripheral length of the outlet end (52) of the dischargeport (50) is Lo; a reference lift amount of the valve body (61) is ho; across sectional area of an outlet side flow path (70) formed between theoutlet end (52) of the discharge port (50) and the valve body (61) isdefined by Ao=Lo×ho; and a hydraulic diameter of the outlet side flowpath (70) is defined by Do=4(Ao/2Lo), and a ratio (Do/Di) of thehydraulic diameter Do of the outlet side flow path (70) to the hydraulicdiameter Di of the inlet end (51) of the discharge port (50) is 0.5 orless.

In the first aspect of the present invention, a discharge port (50) isformed in the fixed side member (45) of the compressor (10). The inletend (51) of the discharge port (50) communicates with the compressionchamber (36). The outlet end (52) of the discharge port (50) isopened/closed by the valve body (61) of the discharge valve (60). In thestate in which the valve body (61) of the discharge valve (60) coversthe outlet end (52) of the discharge port (50), a back-flow of a fluidfrom outside the fixed side member (45) into the discharge port (50) isprevented by the valve body (61). In the state in which the valve body(61) of the discharge valve (60) is lifted from the outlet end (52) ofthe discharge port (50), the fluid in the compression chamber (36) flowsoutside the fixed side member (45) through a gap between the outlet end(52) of the discharge port (50) and the valve body (61).

The peripheral length Li of the inlet end (51) of the discharge port(50) is a wetted perimeter length of the inlet end (51) of the dischargeport (50). Thus, the hydraulic diameter Di of the inlet end (51) of thedischarge port (50) is expressed by the following Equation 01:

Di=4(Ai/Li)   (Equation 01)

In the state in which the valve body (61) of the discharge valve (60) islifted from the outlet end (52) of the discharge port (50), and theoutlet end (52) of the discharge port (50) and the valve body (61) areparallel to each other, the distance between the outlet end (52) of thedischarge port (50) and the valve body (61) (that is, a lift amount ofthe valve body (61)) is uniform around the entire outlet end (52) of thedischarge port (50). Thus, the cross sectional area Ao of the outletside flow path (70) formed between the outlet end (52) of the dischargeport (50) and the valve body (61) is equal to a surface area (i.e.,Lo×h) of a cylinder having a peripheral length equal to the peripherallength Lo of the outlet end (52) of the discharge port (50), and aheight equal to the lift amount h of the valve body (61). However, inthe case, for example, where the discharge valve (60) is a reed valve,the valve body (61) is tilted with respect to the outlet end (52) of thedischarge port (50), and therefore the distance between the outlet end(52) of the discharge port (50) and the valve body (61) is not uniformaround the outlet end (52) of the discharge port (50). To make itpossible, even in such a case, to calculate the cross sectional area Aoof the outlet side flow path (70) similarly to the case where the liftamount of the valve body (61) is uniform around the entire outlet end(52) of the discharge port (50), a typical value of the distance betweenportions of the outlet end (52) of the discharge port (50) and the valvebody (61) is used as a reference lift amount ho. Thus, the crosssectional area Ao of the outlet side flow path (70) is expressed by thefollowing Equation 02:

Ao=Lo×ho   (Equation 02)

In the case where the valve body (61) is parallel to the outlet end (52)of the discharge port (50), the wetted perimeter length of the outletside flow path (70) formed between the outlet end (52) of the dischargeport (50) and the valve body (61) is twice the peripheral length Lo ofthe outlet end (52) of the discharge port (50). By using the referencelift amount ho, the case in which the valve body (61) is tilted withrespect to the outlet end (52) of the discharge port (50) can be treatedsimilarly to the case in which the valve body (61) is parallel to theoutlet end (52) of the discharge port (50). Thus, even in the case wherethe valve body (61) is tilted with respect to the outlet end (52) of thedischarge port (50), the wetted perimeter length of the outlet side flowpath (70) can be approximately 2Lo. Thus, 115 the hydraulic diameter Doof the outlet side flow path (70) is expressed by the following Equation03:

Do=4(Ao/2Lo)=2ho   (Equation 03)

In the first aspect of the present invention, a ratio (Do/Di) of thehydraulic diameter Do of the outlet side flow path (70) to the hydraulicdiameter Di of the inlet end (51) of the discharge port (50) is 0.5 orless (Do/Di<0.5). As shown in Equation 03, the hydraulic diameter Do ofthe outlet side flow path (70) is twice the reference lift amount ho.Thus, in the present invention, the reference lift amount ho of thevalve body (61) of the discharge valve (60) is set to a value accordingto the hydraulic diameter Di of the inlet end (51) of the discharge port(50).

The second aspect of the present invention is that in the first aspectof the present invention, the ratio (Do/Di) of the hydraulic diameter Doof the outlet side flow path (70) to the hydraulic diameter Di of theinlet end (51) of the discharge port (50) is 0.4 or less.

In the second aspect of the present invention, the ratio (Do/Di) of thehydraulic diameter Do of the outlet side flow path (70) to the hydraulicdiameter Di of the inlet end (51) of the discharge port (50) is 0.4 orless (Do/Di<0.4). In the present invention, similarly to the firstaspect of the present invention, the reference lift amount ho of thevalve body (61) of the discharge valve (60) is set to a value accordingto the hydraulic diameter Di of the inlet end (51) of the discharge port(50).

The third aspect of the present invention is that in the first or secondaspect of the present invention, the ratio (Do/Di) of the hydraulicdiameter Do of the outlet side flow path (70) to the hydraulic diameterDi of the inlet end (51) of the discharge port (50) is 0.25 or more.

In the third aspect of the present invention, the reference lift amountho of the valve body (61) of the discharge valve (60) is determined suchthat the ratio (Do/Di) of the “hydraulic diameter Do=4(Ao/2Lo)=2ho ofthe outlet side flow path (70)” to the “hydraulic diameter Di=4(Ai/Li)of the inlet end (51) of the discharge port (50)” is 0.25 or more and0.5 or less (0.25≦Do/Di≦0.5) or 0.25 or more and 0.4 or less(0.25≦Do/Di≦0.4).

The fourth aspect of the present invention is that in any one of thefirst to third aspects of the present invention, the fixed side member(45) is provided with a chamfered portion (56) along the entireperiphery of the outlet end (52) of the discharge port (50).

In the fourth aspect of the present invention, the chamfered portion(56) of the fixed side member (45) is provided along the entireperiphery of the outlet end (52) of the discharge port (50). Thus, thecross sectional area of the flow path of the discharge port (50) closerto the outlet end (52) is gradually increased toward the outlet end (52)of the discharge port (50). In the case where the fixed side member (45)is provided with the chamfered portion (56), the area of the outlet end(52) of the discharge port (50) is larger than in the case where thechamfered portion (56) is not provided. The area of the outlet end (52)of the discharge port (50) is equal to an area (i.e., a pressurereceiving area) of the valve body (61) covering the outlet end (52) ofthe discharge port (50) to which pressure is applied from the dischargeport (50). Thus, if the area of the outlet end (52) of the dischargeport (50) is increased, it means that the pressure receiving area of thevalve body (61) is increased, and the force in a direction separatingthe valve body (61) from the outlet end (52) of the discharge port (50)is increased.

The fifth aspect of the present invention is that in the fourth aspectof the present invention, a height H of the chamfered portion (56) in anaxial direction of the discharge port (50) and a width W of thechamfered portion (56) in a direction orthogonal to the axial directionof the discharge port (50) satisfy a relationship of 0<H/W<0.5.

The larger the width W of the chamfered portion (56) is, the larger thepressure receiving area of the valve body (61) covering the outlet end(52) of the discharge port (50) is. On the other hand, the lower theheight H of the chamfered portion (56) is, the smaller the amount ofincrease in volume of the discharge port (50) caused by the provision ofthe chamfered portion (56) is. The volume of the discharge port (50) isa dead volume which is not changed even if the movable side member (38)rotates. Thus, to improve the efficiency of the compressor (10), asmaller volume of the discharge port (50) is preferable.

In the fifth aspect of the present invention, the chamfered portion (56)formed on the fixed side member (45) has such a shape of which theheight H and the width W satisfy the relationship 0<H/W<0.5. That is,the height H of the chamfered portion (56) is less than half the width Wof the chamfered portion (56). Thus, it is possible to reduce an amountof increase in volume of the discharge port (50), while increasing thepressure receiving area of the valve body (61) covering the outlet end(52) of the discharge port (50).

The sixth aspect of the present invention is that in any one of thefirst to fifth aspects of the present invention, a cross sectional shapeof the discharge port (50) is an oblong or an ellipse.

In the sixth aspect of the present invention, a discharge port (50)whose cross sectional shape is an oblong or an ellipse is formed in thefixed side member (45).

Advantages of the Invention

In the compressor (10) of the present invention, the reference liftamount ho of the valve body (61) of the discharge valve (60) is set suchthat the ratio (Do/Di) of the hydraulic diameter Do of the outlet sideflow path (70) to the hydraulic diameter Di of the inlet end (51) of thedischarge port (50) is 0.5 or less. By setting the lift amount of thevalve body (61) to such a value, the reference lift amount ho of thevalve body (61) becomes a relatively small value, and a vortex generatedat the time when a fluid passes between the outlet end (52) of thedischarge port (50) and the valve body (61) is downsized. Thus, in thepresent invention, the pressure loss of the fluid at the time when thefluid flows out from the discharge port (50) can be reduced, and theefficiency of the compressor (10) can be improved.

If the discharge valve (60) is not closed at an appropriate timing, thefluid discharged from the compression chamber (36) through the dischargeport (50) may flow back to the discharge port (50). On the other hand,if the lift amount of the valve body (61) of the discharge valve (60) isincreased, it takes longer time for the valve body (61) to travel, andthe timing at which the valve body (61) closes the outlet end (52) ofthe discharge port (50) may be delayed from the appropriate timing. Ifthe valve body (61) delays in closing the outlet end (52) of thedischarge port (50), the amount of fluid flowing back to the compressionchamber (36) from outside the fixed side member (45) is increased andthe efficiency of the compressor (10) is reduced.

In contrast, in the present invention, the timing at which the valvebody (61) closes the outlet end (52) of the discharge port (50) isdetermined such that the reference lift amount ho of the valve body (61)is relatively small. Thus, the delay of timing at which the valve body(61) closes the outlet end (52) of the discharge port (50) can bereduced, and the amount of fluid flowing back to the compression chamber(36) from outside the fixed side member (45) can be reduced. As aresult, in view of this point, as well, the efficiency of the compressor(10) can be improved in the present invention.

In particular, in the second aspect of the present invention, thereference lift amount ho of the valve body (61) of the discharge valve(60) is determined such that the ratio (Do/Di) of the hydraulic diameterDo of the outlet side flow path (70) to the hydraulic diameter Di of theinlet end (51) of the discharge port (50) is 0.4 or less. Thus, thedelay in timing at which the valve body (61) closes the outlet end (52)of the discharge port (50) can be further reduced. Accordingly, in thepresent invention, the amount of fluid flowing back to the compressionchamber (36) from outside the fixed side member (45) can be furtherreduced, and as a result, the efficiency of the compressor (10) can befurther improved.

To avoid the back-flow of the fluid to the compression chamber (36), itis only necessary that the outlet end (52) of the discharge port (50) isclosed by the valve body (61) of the discharge valve (60) at anappropriate timing. Thus, if the lift amount of the valve body (61) ofthe discharge valve (60) is equal to or smaller than a certain degree,further reduction in the lift amount of the valve body (61) does notcontribute to an efficiency improvement of the compressor (10).

In contrast, in the third aspect of the present invention, the referencelift amount ho of the valve body (61) of the discharge valve (60) isdetermined such that the ratio (Do/Di) of the “hydraulic diameter Do ofthe outlet side flow path (70)” to the “hydraulic diameter Di of theinlet end (51) of the discharge port (50)” is 0.25 or more and 0.5 orless (0.25≦Do/Di≦0.5) or 0.25 or more and 0.4 or less (0.25≦Do/Di≦0.4).Thus, in the present invention, the reference lift amount ho of thevalve body (61) can be set in a range where the amount of fluid flowingback to the compression chamber (36) can be reduced.

In the fourth aspect of the present invention, the chamfered portion(56) around the entire periphery of the outlet end (52) of the dischargeport (50) is formed on the fixed side member (45). Thus, the area of theoutlet end (52) of the discharge port (50) is increased, compared to thecase in which the chamfered portion (56) is not formed on the fixed sidemember (45). As a result, it is possible to increase the pressurereceiving area of the valve body (61) covering the outlet end (52) ofthe discharge port (50), and possible to increase the force in adirection separating the valve body (61) from the outlet end (52) of thedischarge port (50). Thus, a difference between the internal pressure ofthe compression chamber (36) and the back pressure of the valve body(61) at a moment when the valve body (61) begins to separate from theoutlet end (52) of the discharge port (50) can be reduced, therebyreducing overcompression, i.e., compression of the fluid in thecompression chamber (36) more than necessary, and improving theefficiency of the compressor (10).

The chamfered portion (56) of the fifth aspect of the present inventionhas such a shape of which the height H and the width W satisfy therelationship 0<H/W<0.5. Thus, it is possible to reduce an amount ofincrease in volume of the discharge port (50), while maintaining thepressure receiving area of the valve body (61) covering the outlet end(52) of the discharge port (50).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal cross section of a compressor of an embodiment.

FIG. 2 is a cross section of a compressor mechanism taken along the lineA-A of FIG. 1.

FIG. 3 shows cross sections of a main part of the compressor mechanismalong the longer diameter of a discharge port. FIG. 3A illustrates thestate in which a discharge valve is closed, and FIG. 3B illustrates thestate in which the discharge valve is open.

FIG. 4 is a cross section of a main part of the compressor mechanismalong the shorter diameter of the discharge port.

FIG. 5 is a cross section of the compressor mechanism, illustrating theenlarged main part of the FIG. 3B.

FIG. 6 is a plan view of a front head, and illustrates a portion of thefront head near an outlet end of the discharge port.

FIG. 7A is an oblique view illustrating the shape of actual outlet sideflow path, and FIG. 7B is an oblique view illustrating the shape of avirtual outlet side flow path.

FIG. 8 is a table showing hydraulic diameter rate Do/Di, etc. about aplurality of reference lift amounts ho.

FIG. 9 shows cross sections of a main part of the front head,illustrating a flow of a gas refrigerant flowing out from the dischargeport. FIG. 9A illustrates a cross section taken along the line B-B ofFIG. 4 and a cross section taken along the line C-C of FIG. 3, in thecase where the reference lift amount ho=1.6 mm. FIG. 9B illustrates across section taken along the line B-B of FIG. 4 and a cross sectiontaken along the line C-C of FIG. 3, in the case where the reference liftamount ho=0.8 mm.

FIG. 10 shows graphs of simulation results in the case where thereference lift amount ho=1.4 mm and the case where the reference liftamount ho=1.6 mm. FIG. 10A shows changes between the pressure in thecompression chamber and the lift amount of the valve body while a driveshaft makes one rotation. FIG. 10B shows changes in a flow rate of arefrigerant discharged from the discharge port while the drive shaftmakes one rotation.

FIG. 11 shows graphs of simulation results in the case where thereference lift amount ho=1.2 mm and the case where the reference liftamount ho=1.6 mm. FIG. 11A shows changes between the pressure in thecompression chamber and the lift amount of the valve body while thedrive shaft makes one rotation. FIG. 11B shows changes in a flow rate ofa refrigerant discharged from the discharge port while the drive shaftmakes one rotation.

FIG. 12 shows graphs of simulation results in the case where thereference lift amount ho=1.0 mm and the case where the reference liftamount ho=1.6 mm. FIG. 12A shows changes between the pressure in thecompression chamber and the lift amount of the valve body while a driveshaft makes one rotation. FIG. 12B shows changes in a flow rate of arefrigerant discharged from the discharge port while the drive shaftmakes one rotation.

FIG. 13 shows graphs of simulation results in the case where thereference lift amount ho=0.8 mm and the case where the reference liftamount ho=1.6 mm. FIG. 13A shows changes between the pressure in thecompression chamber and the lift amount of the valve body while thedrive shaft makes one rotation. FIG. 13B shows changes in a flow rate ofa refrigerant discharged from the discharge port while the drive shaftmakes one rotation.

FIG. 14 is a graph showing a relationship between the hydraulic diameterrate Do/Di and a back-flow amount of the refrigerant into thecompression chamber.

FIG. 15 shows cross sections of the front head, illustrating the shapeof the discharge port of the third variation of the embodiment. FIG. 15Aillustrates a cross section corresponding to the B-B cross section ofFIG. 4. FIG. 15B illustrates a cross section corresponding to the C-Ccross section of FIG. 3.

FIG. 16 shows cross sections of the front head, illustrating the shapeof the discharge port of the fourth variation of the embodiment. FIG.16A illustrates a cross section corresponding to the B-B cross sectionof FIG. 4. FIG. 16B illustrates a cross section corresponding to the C-Ccross section of FIG. 3.

FIG. 17 is a plan view of a front head of the fifth variation of theembodiment, and illustrates a portion of the front head near an outletend of the discharge port.

FIG. 18 is a cross section of a compressor mechanism of the sixthvariation of the embodiment, and illustrates a cross sectioncorresponding to FIG. 2.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described in detail basedon the drawings. The following embodiments and variations are merelypreferred examples in nature, and are not intended to limit the scope,applications, and use of the invention,

A compressor (10) of the present embodiment is provided in a refrigerantcircuit which performs a vapor compression refrigeration cycle, and thecompressor (10) suctions a refrigerant evaporated in an evaporator andcompresses the refrigerant.

—General Structure of Compressor—

As shown in FIG. 1, the compressor (10) of the present embodiment s ahermetic compressor which accommodates, in a casing (11), a compressormechanism (30) and an electric motor (20).

The casing (11) is a cylindrical closed container, standing upright. Thecasing (11) has a cylindrical barrel (12) and a pair of end plates (13,14) which close the both ends of the barrel (12). A suction pipe (15) isattached to a lower portion of the barrel (12). A discharge pipe (16) isattached to the upper end plate (13).

The electric motor (20) is positioned above the compressor mechanism(30). The electric motor (20) has a stator (21) and a rotor (22). Thestator (21) is fixed to the barrel (12) of the casing (11). The rotor(22) is attached to a drive shaft (23) of the compressor mechanism (30),described later.

The compressor mechanism (30) is positioned at a lower portion in thecasing (11). The compressor mechanism (30) is a so-called oscillatingpiston type rotary fluid machine. The compressor mechanism (30) has afront head (31), a cylinder (32), and a rear head (33).

The cylinder (32) is a disk-shaped thick member (see FIG. 2). A circularhole which forms a compression chamber (36) together with a piston (38),described later, is formed at a central portion of the cylinder (32).The front head (31) is a plate-like member which closes the upper endsurface of the cylinder (32). A main bearing (31 a) which supports thedrive shaft (23) is arranged to project from a central portion of thefront head (31). The rear head (33) is a plate-like member which closesthe lower end surface of the cylinder (32). An auxiliary bearing (33 a)which supports the drive shaft (23) is arranged to project from acentral portion of the rear head (33).

The cylinder (32) is fixed to the barrel (12) of the casing (11). Thefront head (31), the cylinder (32), and the rear head (33) are fastenedtogether with bolts, and form a fixed side member (45).

The compressor mechanism (30) has a drive shaft (23). The drive shaft(23) has a main shaft (24) and an eccentric portion (25). The eccentricportion (25) is positioned at a lower portion of the main shaft (24).The eccentric portion (25) is in a columnar shape with a diameter largerthan the diameter of the main shaft (24), and is eccentric with respectto the main shaft (24). Although not shown, an oil supply path is formedin the drive shaft (23). The lubricating oil accumulated in the bottomof the casing (11) is supplied to sliding portions of the bearings (31a, 33 a) and the compressor mechanism (30) through the oil supply path.

As also shown in FIG. 2, the compressor mechanism (30) has a piston (38)as a movable side member and a blade (43).

The piston (38) is in a slightly thick cylindrical shape. The eccentricportion (25) of the drive shaft (23) is rotatably fitted in the piston(38). An outer circumferential surface (39) of the piston (38) slides onan inner circumferential surface (35) of the cylinder (32). In thecompressor mechanism (30), the compression chamber (36) is formedbetween the outer circumferential surface (39) of the piston (38) andthe inner circumferential surface (35) of the cylinder (32).

The blade (43) is a flat plate-like member projecting from the outercircumferential surface (39) of the piston (38), and is integrallyformed with the piston (38). The blade (43) separates the compressionchamber (36) into a high-pressure chamber (36 a) and a low-pressurechamber (36 b).

The compressor mechanism (30) has a pair of bushes (41). The pair ofbushes (41) are fitted in a bush groove (40) of the cylinder (32), andsandwich the blade (43) from both sides. The blade (43) integrallyformed with the piston (38) is supported on the cylinder (32) via thebushes (41).

The cylinder (32) is provided with a suction port (42) that penetratesthe cylinder (32) in the radius direction. The suction port (42)communicates with the low-pressure chamber (36 b) of the compressionchamber (36). One end of the suction port (42) is open on the innercircumferential surface (35) of the cylinder (32). The open end of thesuction port (42) which is open on the inner circumferential surface(35) is located near the bushes (41) (on the right side of the bushes(41) in FIG. 2). On the other hand, the suction pipe (15) is inserted inthe other end of the suction port (42).

A discharge port (50) is formed in the front head (31). The dischargeport (50) is a through hole which penetrates the front head (31) in thethickness direction of the front head (31) (see FIG. 1). The dischargeport (50) communicates with the high-pressure chamber (36 a) of thecompression chamber (36). The open end of the discharge port (50) whichis open on the lower surface of the front head (31) is located oppositeto the suction port (42) with respect to the bushes (41) (on the leftside of the bushes (41) in FIG. 2). The shape of the discharge port (50)will be described in detail later.

The front head (31) is provided with a discharge valve (60), which is areed valve. As shown in FIG. 3, the discharge valve (60) is attached tothe upper surface of the front head (31). The discharge valve (60) has avalve body (61), a valve guard (62), and a securing pin (63).

The valve body (61) is an elongated, thin fiat plate-like member. Amaterial for the valve body (61) is spring steel, for example. The valvebody (61) is provided such that its end portion covers an outlet end(52) of the discharge port (50). When the discharge valve (60) is in adosed state, a front surface (61 a) of the valve body (61) is broughtinto tight contact with a periphery (52 a) of the outlet end (52) of thedischarge port (50). The valve guard (62) is a slightly thick metallicmember with a high stiffness. The valve guard (62) is in an elongatedplate-like shape corresponding to the shape of the valve body (61).Further, an end portion of the valve guard (62) is slightly curvedupward. The valve guard (62) is arranged to overlap the valve body (61).The proximal portion of the valve guard (62) and the proximal portion ofthe valve body (61) are fixed to the front head (31) with the securingpin (63).

As shown in FIG. 3A, the discharge port (50) is closed in the state inwhich the valve body (61) covers the outlet end (52) of the dischargeport (50). On the other hand, as shown in FIG. 3B and FIG. 4, thedischarge port (50) is open in the state in which the valve body (61) islifted from the outlet end (52) of the discharge port (50).

As described above, the compressor mechanism (30) of the presentembodiment is a rotary fluid machine which has the cylinder (32), thefront head (31) and the rear head (33) which serve as closing membersfor closing end portions of the cylinder (32), the piston (38) which isaccommodated in the cylinder (32) and eccentrically rotates, and theblade (43) which separates the compression chamber (36) formed betweenthe cylinder (32) and the piston (38) into a low-pressure side and ahigh-pressure side.

—Operation of Compressor—

Operation of the compressor (10) will be described with reference toFIG. 2.

When the electric motor (20) is turned on, the drive shaft (23) rotatesin a clockwise direction in FIG. 2. When the drive shaft (23) rotates,the piston (38) integrally formed with the blade (43) oscillates andeccentrically rotates. When the piston (38) moves, a low-pressure gasrefrigerant is suctioned into the low-pressure chamber (36 b) of thecompression chamber (36) through the suction port (42), and at the sametime, a gas refrigerant that is present in the high-pressure chamber (36a) of the compression chamber (36) is compressed.

At this moment, gas pressure (pressure in the dome) in the internalspace of the casing (11) is applied to a back surface (61 b) of thevalve body (61) of the discharge valve (60). Thus, as long as the gaspressure in the high-pressure chamber (36 a) is lower than the pressurein the dome, the discharge valve (60) is in the closed state as shown inFIG. 3A. When the piston (38) moves, and the gas pressure in thehigh-pressure chamber (36 a) gradually increases and exceeds thepressure in the dome, the end portion of the valve body (61) of thedischarge valve (60) separates from the outlet end (52) of the dischargeport (50). As a result, the discharge valve (60) is open as shown inFIG. 3B.

When the discharge valve (60) is open, the as refrigerant in thehigh-pressure chamber (36 a) passes through the discharge port (50) andflows between the outlet end (52) of the discharge port (50) and thevalve body (61), and is discharged to the internal space of the casing(11) (that is, outside the compressor mechanism (30)). The high-pressuregas refrigerant discharged from the compressor mechanism (30) passesthrough the discharge pipe (16) and is led outside the casing (11).

—Shape of Discharge Port—

The shape of the discharge port (50) will be described in detail withreference to FIG. 5 and FIG. 6.

The discharge port (50) is a straight through hole which penetrates thefront head (31) in the plate thickness direction (see FIG. 5). An inletend (51) of the discharge port (50) is open on the front surface (i.e.,the surface facing the cylinder (32)) of the front head (31). On theother hand, the outlet end (52) of the discharge port (50) is open onthe back surface (i.e., the surface opposite to the surface facing thecylinder (32)) of the front head (31). On the back surface of the fronthead (31), a portion around the outlet end (52) of the discharge port(50) is raised from its surrounding area, and serves as a seat portion(55).

The cross section of the flow path of the discharge port (50) (i.e., thecross section orthogonal to the axial direction of the discharge port(50)) is in an oblong shape (see FIG. 6). The discharge port (50) isarranged such that its shorter diameter is along the radius dimension ofthe inner circumferential surface (35) of the cylinder (32) (see FIG.2).

The front head (31) is provided with a chamfered portion (56) along theperiphery (52 a) of the outlet end (52) of the discharge port (50). Thechamfered portion (56) is formed around the entire periphery of theoutlet end (52) of the discharge port (50) (see FIG. 6). The chamferedportion (56) is formed such that the height H in the axial direction ofthe discharge port (50) and the width W in a direction orthogonal to theaxial direction of the discharge port (50) are respectively uniformaround the entire periphery of the chamfered portion (56) (see FIG. 5).In the present embodiment, the height H and the width W of the chamferedportion (56) satisfy the following formula: 0<H/W<0.5. That is, theheight H of the chamfered portion (56) is less than half of the width Wof the chamfered portion (56) (0<H<W/2).

A portion of the discharge port (50) at a position lower than thechamfered portion (56) forms a main pass (53). The cross section of theflow path of the main pass (53) is in an oblong shape having an arcportion with a curvature radius Ri and a straight portion with a lengthLs. Further, the shape of the cross section of the flow path of the mainpass (53) is uniform along the entire length thereof. That is, thelonger diameter length D₁ and the shorter diameter length D₂ of thecross section of the flow path of the main pass (53) are respectivelyuniform along the entire length of the main pass (53). Accordingly, theshape of the inlet end (51) of the discharge port (50) is also in anoblong shape having an arc portion with the curvature radius Ri and astraight portion with the length Ls.

The shape of the outlet end (52) of the discharge port (50) is in anoblong shape slightly larger than that of the inlet end (51) of thedischarge port (50). Specifically, the shape of the outlet end (52) ofthe discharge port (50) is in an oblong shape having an arc portion witha curvature radius defined by Ro=Ri+W and a straight portion with alength Ls.

At the inlet end (51) of the discharge port (50) of the presentembodiment, the curvature radius of the arc portion is defined by Ri=2.1mm, and the length of the straight portion is defined by Ls=5.3 mm. Atthe outlet end (52) of the discharge port (50), the curvature radius ofthe arc portion is defined by Ro=3.1 mm, and the length of the straightportion is defined by Ls=5.3 mm. At the chamfered portion (56) of thedischarge port (50), a ratio of the height H to the width W (H/W) is 0.5(H/W=0.5). The figures shown herein are merely an example.

If the front head (31) is provided with the chamfered portion (56), anarea of the outlet end (52) of the discharge port (50) is larger than inthe case in which the front head (31) is not provided with the chamferedportion (56). The area of the outlet end (52) of the discharge port (50)is equal to an area (i.e., a pressure receiving area) of a portion ofthe front surface (61 a) of the valve body (61) to which pressure isapplied from the e discharge port (50). Thus, if the area of the outletend (52) of the discharge port (50) is increased, it means that thepressure receiving area of the valve body (61) is increased, and theforce in a direction separating the valve body (61) from the outlet end(52) of the discharge port (50) is increased.

If the force in the direction separating the valve body (61) from theoutlet end (52) of the discharge port (50) is increased, a differencebetween the “gas pressure in the compression chamber (36)” and the “gaspressure applied to the back surface (61 b) of the valve body (61)” at amoment when the valve body (61) begins to separate from the outlet end(52) of the discharge port (50) becomes small. Thus, loss (i.e., loss byovercompression) caused by compressing the gas refrigerant in thecompression chamber (36) more than necessary is reduced.

On the other hand, on condition that the width W of the chamferedportion (56) is the same, the lower the height H of the chamferedportion (56) is, the smaller the amount of increase in volume of thedischarge port (50) due to the provision of the chamfered portion (56)is. The volume of the discharge port (50) is a dead volume which is notchanged even if the piston (38) rotates. Thus, to improve the efficiencyof the compressor (10), it is preferable to reduce the volume of thedischarge port (50) as much as possible.

Thus, in the compressor (10) of the present embodiment, the height H ofthe chamfered portion (56) is set to less than half of the width W ofthe chamfered portion (56), considering an efficiency improvement causedby a reduction of the loss by overcompression, and an efficiencydecrease caused by an increase of the dead volume.

—Lift Amount of Valve Body of Discharge Valve—

In the compressor (10) of the present embodiment, a lift amount of thevalve body (61) of the discharge valve (60) is determined such thatpressure loss of the gas refrigerant at the time when the gasrefrigerant is discharged from the compressor mechanism (30) can bereduced to low level, and such that a reduction in efficiency of thecompressor (10) due to delay in closing the valve body (61) of thedischarge valve (60) can be reduced. As will be described in detaillater, in the compressor (10) of the present embodiment, a referencelift amount ho of the valve body (61) of the discharge valve (60) isdetermined, based on a hydraulic diameter Di of the inlet end (51) ofthe discharge port (50).

<Hydraulic Diameter Di of Inlet End of Discharge Port>

As described above, the inlet end (51) of the discharge port (50) is inan oblong shape having the arc portion with the curvature radius Ri andthe straight portion with the length Ls. Thus, the length (i.e., theperipheral length of the periphery (51 a) of the inlet end (51) of thedischarge port (50) is expressed by Equation 1 shown below, and the areaAi thereof is expressed by Equation 2 shown below. The peripheral lengthLi of the inlet end (51) of the discharge port (50) is a wettedperimeter length of the inlet end (51) of the discharge port (50). Thus,the hydraulic diameter Di of the inlet end (51) of the discharge port(50) is expressed by Equation 3 below. Equation 3 is the same asEquation 01 described above.

Li=2πRi+2Ls   (Equation 1)

Ai=πRi ²+2Ri·Ls   (Equation 2)

Di=4(Ai/Li)   (Equation 3)

The inlet end (51) of the discharge port (50) of the present embodimenthas the arc portion with the curvature radius Ri of 2.1 mm, and thestraight portion with the length Ls of 5.3 mm. Thus, the peripherallength Li is 23.8 mm; the area Al is 36.1 mm²; and the hydraulicdiameter Di is 6.1 mm.

<Reference Lift Amount ho of Valve Body of Discharge Valve>

As shown in FIG. 5, the reference lift amount ho of the valve body (61)of the discharge valve (60) is the maximum lift amount of the valve body(61) on a center line CL of the discharge port (50). That is, thereference lift amount ho is a distance from the “outlet end (52) of thedischarge port (50)” to the “front surface (61 a) of the valve body(61)” on the center line CL of the discharge port (50) in the state inwhich the entire back surface (61 b) of the valve body (61) touches thevalve guard (62).

The center line CL of the discharge port (50) is a straight line passingan intersection point of the longer diameter and the shorter diameter ofthe inlet end (51) of the discharge port (50) and an intersection pointof the longer diameter and the shorter diameter of the outlet end (52)of the discharge port (50). The center line CL is orthogonal to theinlet end (51) and the outlet end (52) of the discharge port (50).

The front surface (61 a) of the valve body (61) is tilted with respectto the outlet end (52) of the discharge port (50) in the state in whichthe entire back surface (61 b) of the valve body (61) touches the valveguard (62). Thus, as shown in FIG. 5, the distance (that is, the liftamount of the valve body (61)) from the outlet end (52) of the dischargeport (50) to the front surface (61 a) of the valve body (61) has amaximum value of h₁, and a minimum value of h₂.

<Hydraulic Diameter Do of Outlet Side Flow Path>

In the state in which the valve body (61) of the discharge valve (60) islifted from the outlet end (52) of the discharge port (50), an outletside flow path (70) is formed between the outlet end (52) of thedischarge port (50) and the valve body (61). The gas refrigerantdischarged from the discharge port (50) passes through the outlet sideflow path (70).

As described above, the outlet end (52) of the discharge port (50) is inan oblong shape. Further, as shown in FIG. 5, in the state in which thevalve body (61) is lifted from the outlet end (52) of the discharge port(50), the front surface (61a) of the valve body (61) is tilted withrespect to the outlet end (52) of the discharge port (50). Thus, theoutlet side flow path (70) has a cross-sectional shape as shown in FIG.7A (that is, the same shape as a side surface of a tubular object havinga top surface tilted with respect to its bottom surface. A lowerperiphery (72) of the outlet side flow path (70) is in the same oblongshape as the periphery (52 a) of the outlet end (52) of the dischargeport (50). On the other hand, an upper periphery (71) of the outlet sideflow path (70) is in the shape obtained by projecting the periphery (52a) of the outlet end (52) of the discharge port (50) to the frontsurface (61 a) of the valve body (61). Further, the height of the outletside flow path (70) has a maximum value of h₁, and a minimum value ofh₂.

The front surface (61 a) of the valve body (61) is not curved and issubstantially flat in the state in which the entire back surface (61 b)of the valve body (61) touches the valve guard (62). Thus, the referencelift amount ho of the valve body (61) is substantially equal to anaverage value ((h₁+h₂)/2) of the maximum value h₁ and the minimum valueh₂ of the lift amount of the valve body (61). Therefore, a crosssectional area of the actual outlet side flow path (70) shown in FIG. 7Ais substantially equal to the cross sectional area of a virtual outletside flow path (75) shown in FIG. 7B.

In the virtual outlet side flow path (75) shown in FIG. 7B, the frontsurface (61 a) of the valve body (61) is parallel to the outlet end (52)of the discharge port (50), and in the case where the distance from theoutlet end (52) of the discharge port (50) to the front surface (61 a)of the valve body (61) is the reference lift amount ho, the virtualoutlet side flow path (75) is a flow path formed between the outlet end(52) of the discharge port (50) and the valve body (61). The crosssectional shape of the virtual outlet side flow path (75) is the same asa side surface of a tubular object having a top surface parallel to itsbottom surface.

In the present embodiment, the virtual outlet side flow path (75) shownin FIG. 7B is treated as being substantially equivalent to the actualoutlet side flow path (70) shown in FIG. 7A. Further, the hydraulicdiameter of the actual outlet side flow path (70) shown in FIG. 7A istreated as being substantially equal to the hydraulic diameter of thevirtual outlet side flow path (75) shown in FIG. 7B, and is calculatedbased on the following Equations 4-6.

The shape of the outlet end (52) of the discharge port (50) is an oblongshape having an arc portion with a curvature radius Ro and a straightportion with a length Ls. Thus, the length (i.e., the peripheral lengthLo) of the periphery (52 a) of the outlet end (52) of the discharge port(50) is expressed by Equation 4 shown below.

Lo=2πRo+2Ls   (Equation 4)

Each of an upper periphery (76) and a lower periphery (77) of thevirtual outlet side flow path (75) is in the same shape as the outletend (52) of the discharge port (50), similarly to the lower periphery(72) of the actual outlet side flow path (70). The peripheral length ofthe virtual outlet side flow path (75) is equal to the peripheral lengthLo of the outlet end (52) of the discharge port (50). Thus, a crosssectional area Ao of the virtual outlet side flow path (75) is expressedby Equation 5. Equation 5 is the same as Equation 02 described above.

Ao=Lo×ho   (Equation 5)

The wetted perimeter length of the virtual outlet side flow path (75) isa sum of its upper peripheral length and its lower peripheral length.Thus, the wetted perimeter length of the virtual outlet side flow path(75) is 2Lo. The hydraulic diameter Do of the virtual outlet side flowpath (75) is therefore expressed by Equation 6. In the presentembodiment, the hydraulic diameter of the actual outlet side flow path(70) is considered as being equal to the hydraulic diameter Docalculated by Equation 6, Equation 6 is the same as Equation 03described above.

Do=4(Ao/2Lo)=2ho   (Equation 6)

The outlet end (52) of the discharge port (50) of the present embodimenthas the arc portion with a curvature radius of Ro=3.1 mm, and thestraight portion with a length of Ls=5.3 mm. Thus, the peripheral lengthLo of the outlet end (52) of the discharge port (50) is 30.1 mm. On theother hand, the cross sectional area Ao and the hydraulic diameter Do ofthe virtual outlet side flow path (75) are a function of the referencelift amount ho. FIG. 8 shows the cross sectional area Ao of the flowpath and the hydraulic diameter Do thereof in each of the cases wherethe reference lift amount ho is 0.8 mm, 1.0 mm, 1.2 mm, 1.4 mm and 1.6mm.

<Hydraulic Diameter Rate Do/Di>

In the compressor (10) of the present embodiment, the reference liftamount ho of the valve body (61) of the discharge valve (60) isdetermined such that the ratio (Do/Di) of the hydraulic diameter Do ofthe outlet side flow path (70) to the hydraulic diameter Di of the inletend (51) of the discharge port (50) satisfies the relationship definedby the Formula 7 shown below. Equation 6 shows Do=2ho. Thus, in thecompressor (10) of the present embodiment, the reference lift amount hoof the valve body (61) of the discharge valve (60) is set to a valuewithin a range defined by Formula 8.

0.25≦Do/Di≦0.5   (Formula 7)

Di/8≦ho≦Di/4   (Formula 8)

FIG. 8 shows the hydraulic diameter Do of the outlet side flow path (70)and values of the hydraulic diameter rate Do/Di in each of the caseswhere the reference lift amount ho is 0.8 mm, 1.0 mm, 1.2 mm, 1.4 mm and1.6 mm. In each of the cases where the reference lift amount ho is 0.8mm, 1.0 mm, 1.2. mm and 1.4 mm, the hydraulic diameter rate Do/Di is0.25 or more and 0.5 or less. On the other hand, in the case where thereference lift amount ho is 1.6 mm, the hydraulic diameter rate Do/Di islarger than 0.5. Thus, each of the cases where the reference lift amountho is 0.8 mm, 1.0 mm, 1.2 mm and 1.4 mm is an embodiment of the presentapplication, whereas the case in which the reference lift amount ho is1.6 mm is not an embodiment of the present application, but acomparative example.

The values of the hydraulic diameter rate Do/Di shown in FIG. 8 werecalculated using Equation 9 below. Equation 9 can be obtained bysubstituting Equation 1 to Equation 3 and Equation 6 for Do/Di.

$\begin{matrix}\begin{matrix}{{{Do}\text{/}{Di}} = {{2{ho}\text{/}4( {{Ai}\text{/}{Li}} )} = {{{ho} \cdot {Li}}\text{/}2{Ai}}}} \\{= {{{ho}( {{\pi \; {Ri}} + {Ls}} )}\text{/}{{Ri}( {{\pi \; {Ri}} + {2{Ls}}} )}}}\end{matrix} & ( {{Equation}\mspace{14mu} 9} )\end{matrix}$

—Range of Values of Hydraulic Diameter Rate Do/Di—

The reason why it is preferable to determine the reference lift amountho of the valve body (61) of the discharge valve (60) such that thehydraulic diameter rate Do/Di is 0.25 or more and 0.5 or less will beexplained.

<Pressure Loss of Discharged Refrigerant>

As shown in FIG. 9, the gas refrigerant discharged from the compressormechanism (30) is ejected first from the outlet end (52) of thedischarge port (50) to the valve body (61) of the discharge valve (60),and then collides with the front surface (61a) of the valve body (61)and changes its flow direction to spread around the outlet end (52) ofthe discharge port (50).

As shown in FIG. 9A, in the case where the reference lift amount ho=1.6mm (0.5<Do/Di), a relatively large vertical vortex is generated aroundthe outlet end (52) of the discharge port (50). The vertical vortexinterrupts a flow of the gas refrigerant that is about to flow out fromthe outlet side flow path (70) (that is, a gap between the outlet end(52) of the discharge port (50) and the valve body (61)). Thus, the gasrefrigerant can pass through only a small part of the outlet side flowpath (70) closer to the valve body (61). Thus, in spite of the fact thatthe cross sectional area of the outlet side flow path (70) is relativelylarge, the pressure loss of the gas refrigerant when the gas refrigerantis passing through the outlet side flow path (70) is not much reduced.

On the other hand, as shown in FIG. 9B, in the case where the referencelift amount ho=0.8 mm (0.25≦Do/Di≦0.5), a vertical vortex is notsubstantially generated around the outlet end (52) of the discharge port(50). The gas refrigerant collides with the valve body (61) immediatelyafter it is ejected from the outlet end (52) of the discharge port (50)and changes its flow direction, and passes through almost entire part ofthe outlet side flow path (70). Thus, in spite of the fact that thecross sectional area of the outlet side flow path (70) is smaller thanin the case where the reference lift amount ho=1.6 mm, the pressure lossof the gas refrigerant when the gas refrigerant passes through theoutlet side flow path (70) is almost equal to the pressure loss in thecase where the reference lift amount ho=1.6 mm.

<Pulsation of Discharged Refrigerant>

The vertical vortex shown in FIG. 9A is generated and disappears severaltimes in one discharge process. As mentioned above, the vertical vortexinterrupts a flow of the gas refrigerant that is about to flow out fromthe outlet side flow path (70). Thus, every time the vertical vortex isgenerated and disappears, a flow rate of the gas refrigerant flowing outfrom the outlet side flow path (70) changes.

FIG. 10B, FIG. 11B, FIG. 12B and FIG. 13B show changes in a mass flowrate (that is, a discharge flow rate) of the gas refrigerant dischargedfrom the discharge port (50) of the compressor mechanism (30). Forexample, in FIG. 10B, the discharge flow rate rapidly increases when thedischarge valve (60) starts to separate from the outlet end (52) of thedischarge port (50) at a point where a rotation angle of the drive shaft(23) is around 230°. The discharge flow rate shows a maximum value at apoint where the rotation angle of the drive shaft (23) is around 250°.After that, the discharge flow rate relatively significantly changes inspite of the fact that the lift amount of the valve body (61) isapproximately uniform. These changes in the discharge flow rate in thedischarge process are caused by the generation and disappearance of thevertical vortex formed around the outlet end (52) of the discharge port(50).

It is preferable that the changes in the discharge flow rate are assmall as possible since such changes lead to vibrations of thecompressor (10) and noise. As shown in FIG. 10B, FIG. 11B, FIG. 12B andFIG. 13B, the range of the discharge flow rate in the discharge processis smaller in each of the cases where the reference lift amount ho is0.8 mm, 1.0 mm, 1.2 mm and 1.4 mm, than in the case where the referencelift amount ho is 1.6 mm. Further, the range of the discharge flow ratein the discharge process is reduced as the reference lift amount hobecomes smaller. Thus, in the compressor (10) of the present embodiment,the reference lift amount ho of the valve body (61) of the dischargevalve (60) is determined such that the hydraulic diameter rate Do/Di is0.5 or less.

<Delay in Closing Discharge Valve>

When the discharge valve (60) is opened/closed, the valve body (61) iselastically deformed, causing the end portion of the valve body (61) tomove. The larger the reference lift amount ho of the valve body (61) is,the longer the traveling distance of the valve body (61) is when thedischarge valve (60) is opened/closed. The longer traveling distance ofthe valve body (61) requires longer time to open/close the dischargevalve (60). Thus, if the reference lift amount ho of the valve body (61)is excessively large, a phenomenon (referred to as a “delay-in-closingphenomenon”) occurs in which the valve body (61) is separated from theoutlet end (52) of the discharge port (50) even at a moment when thedischarge valve (60) is supposed to be closed. For example, as shown inFIG. 10A, in the case where the reference lift amount ho is 1.6 mm, thelift amount of the valve body (61) is about 0.6 mm even at a moment whenthe rotation angle of the drive shaft (23) reaches 360°.

When the delay-in-closing phenomenon occurs, the compression chamber(36) in an early stage of the compression process communicates with theinternal space of the casing (11) through the discharge port (50), andas a result, the high-pressure gas refrigerant in the internal space ofthe casing (11) flows back to the compression chamber (36) through thedischarge port (50). Thus, when the delay-in-closing phenomenon occurs,the mass flow rate of the refrigerant discharged from the compressormechanism (30) per unit time is reduced, and that leads to a reductionin efficiency of the compressor (10). To avoid the reduction inefficiency of the compressor (10) caused by the delay-in-closingphenomenon of the discharge valve (60), it is preferable that thereference lift amount ho of the valve body (61) of the discharge valve(60) is as small as possible.

However, if the reference lift amount ho of the valve body (61) of thedischarge valve (60) is too small, the pressure loss of the refrigerantwhen the refrigerant is discharged from the compressor mechanism (30)may become too large. On the other hand, as shown in FIG. 14, in thecase where the hydraulic diameter rate Do/Di is relatively large, theback-flow amount of the refrigerant into the compression chamber (36) isgradually reduced as the hydraulic diameter rate Do/Di becomes smaller.However, in the case where the hydraulic diameter rate Do/Di is lessthan 0.25, the back-flow amount of the refrigerant into the compressionchamber (36) is not reduced much even when the hydraulic diameter rateDo/Di becomes smaller. Thus, in the compressor (10) of the presentembodiment, the reference lift amount ho of the valve body (61) of thedischarge valve (60) is determined such that the hydraulic diameter rateDo/Di is 0.25 or more.

—Advantages of Embodiment—

In the compressor (10) of the present embodiment, the reference liftamount ho of the valve body (61) of the discharge valve (60) isdetermined such that the hydraulic diameter rate Do/Di is 0.25 or moreand 0.5 or less. It is thus possible to reduce time necessary foropening/closing the valve body (61) by reducing the reference liftamount ho of the valve body (61), without increasing the pressure lossof the refrigerant (the discharged refrigerant) discharged from thecompressor mechanism (30). If the valve body (61) is opened/closed withless time, the amount of the refrigerant flowing back to the compressionchamber (36) due to a delay in closing the valve body (61) reduced.Thus, in the present embodiment, it is possible to improve theefficiency of the compressor (10) by reducing the amount of therefrigerant flowing back to the compression chamber (36), while avoidingthe efficiency reduction of the compression chamber (36) due to anincrease in the pressure loss of the discharged refrigerant.

If the rotational speed of the compressor mechanism (30) is increased,time necessary for performing one discharge process is shortened. Thus,the higher the rotational speed of the compressor mechanism (30) is, themore it is necessary to reduce time necessary for opening/closing thevalve body (61). By determining the reference lift amount ho of thevalve body (61) of the discharge valve (60) such that the hydraulicdiameter rate Do/Di is 0.25 or more and 0.5 or less, it is possible toreduce adverse effects caused by a delay in closing the valve body (61),even in the case where the rotational speed of the compressor mechanism(30) is very high (for example, 120 or more revolutions per second).

Further, in the compressor (10) of the present embodiment, the height Hand the width W of the chamfered portion (56) satisfy the relationshipof 0<H/W<0.5. That is, in the present embodiment, the chamfered portion(56) has a relatively gentle inclination. Thus, the area (i.e., thepressure receiving area) of the portion of the front surface (61 a) ofthe valve body (61) to which pressure is applied from the discharge port(50) can be increased, and an increase in the volume of the dischargeport (50) due to the provision of the chamfered portion (56) can bereduced. As a result, in the present embodiment, the efficiencyreduction of the compressor (10) due to an increase in the dead volumecan be reduced, and the efficiency of the compressor (10) can beimproved due to a reduction in loss by overcompression.

First Variation of Embodiment

In the compressor (10) of the present embodiment, it is more preferableto determine the reference lift amount ho of the valve body (61) of thedischarge valve (60) such that the hydraulic diameter rate Do/Di is 0.25or more and 0.4 or less.

If the valve body (61) is separated from the seat portion (55) at thepoint when the rotation angle of the drive shaft (23) reaches 360°, theinternal space of the casing (11) communicates with the suction port(42) through the discharge port (50) and the compression chamber (36),and this may result in an excess amount of refrigerant flowing back tothe compression chamber (36) from the internal space of the casing (11).

On the other hand, as shown in FIG. 11, in the case where the hydraulicdiameter rate Do/Di is 0.4, the lift amount of the valve body (61)becomes zero at the point when the rotation angle of the drive shaft(23) reaches 360°. That is, the discharge port (50) is completely closedat the point when the rotation angle of the drive shaft (23) reaches360°. Further, as shown in FIG. 12 and FIG. 13, the smaller thehydraulic diameter rate Do/Di becomes, the earlier the lift amount ofthe valve body (61) becomes zero.

Thus, by determining the reference lift amount ho of the valve body (61)of the discharge valve (60) such that the hydraulic diameter rate Do/Diis 0.25 or more and 0.4 or less as in the present variation, it ispossible to more reliably reduce the amount of refrigerant flowing backto the compression chamber (36). This will be explained with referenceto FIG. 14.

Vmin shown in FIG. 14 is a lower limit of the amount of refrigerantflowing back to the compression chamber (36). That is, the amount ofrefrigerant flowing back to the compression chamber (36) cannot bereduced to zero because of the structure of the compressor (10). Forexample, in reality, it is impossible to reduce the volume of thedischarge port (50) to zero, and the amount exceeding the lower limitVmin is an amount of refrigerant flowing back to the compression chamber(36) which can be reduced. As shown in FIG. 14, the amount ofrefrigerant flowing back to the compression chamber (36) which can bereduced is ΔV₁ in the case where the hydraulic diameter rate Do/Di is0.53, and ΔV₂ in the case where the hydraulic diameter rate Do/Di is0.4.

ΔV₂ is less than half ΔV₁(ΔV₂<ΔV₁/2). Thus, by determining the referencelift amount ho of the valve body (61) of the discharge valve (60) suchthat the hydraulic diameter rate Do/Di is 0.4 or less, the amount ofrefrigerant flowing back to the compression chamber (36) can besignificantly reduced. Thus, in the present variation, the efficiency ofthe compressor (10) can be reliably improved.

Second Variation of Embodiment

As shown in FIG. 8, in the case where the reference lift amount ho ofthe valve body (61) of the discharge valve (60) is determined such thatthe hydraulic diameter rate Do/Di is 0.4, the cross sectional area Ao ofthe virtual outlet side flow path (75) is substantially equal to thearea Al of the inlet end (51) of the discharge port (50). In the casewhere the reference lift amount ho of the valve body (61) of thedischarge valve (60) is determined such that the hydraulic diameter rateDo/Di is less than 0.4, the cross sectional area Ao of the virtualoutlet side flow path (75) is smaller than the area Ai of the inlet end(51) of the discharge port (50). Thus, in the compressor (10) of thepresent embodiment, it is preferable to determine the reference liftamount ho of the valve body (61) of the discharge valve (60) such thatthe cross sectional area Ao of the virtual outlet side flow path (75) isless than or equal to the area Ai of the inlet end (51) of the dischargeport (50) (Ao≦Ai).

Third Variation of Embodiment

As shown in FIG. 15, in the compressor (10) of the present embodiment,the cross sectional area of the main pass (53) of the discharge port(50) may be gradually increased from the inlet end (51) to the outletend (52) of the discharge port (50). In the present variation, the wallsurface forming the main pass (53) of the discharge port (50) is aconical surface about the center line CL of the discharge port (50).Further, in FIG. 15, the longer diameter length D₁₂ of the upper end ofthe main pass (53) is longer than the longer diameter length D₁₁ of thelower end of the main pass (53), and the shorter diameter length D₂₂ ofthe upper end of the main pass (53) is longer than the longer diameterlength D₂₁ of the lower end of the main pass (53).

Fourth Variation of Embodiment

As shown in FIG. 16, in the compressor (10) of the present embodiment,the chamfered portion (56) may be omitted. The shape of the crosssection of the flow path of the discharge port (50) according to thepresent variation is a uniform oblong shape from the inlet end (51) tothe outlet end (52) of the discharge port (50).

Fifth Variation of Embodiment

As shown in FIG. 17, in the compressor (10) of the present embodiment,the cross sectional shape of the discharge port (50) may be an ellipse.In the present variation, too, the front head (31) is provided with achamfered portion (56) around the entire periphery (52 a) of the outletend (52) of the discharge port (50). Similarly to the chamfered portion(56) shown in FIG. 5 and FIG. 6, the height H and the width W of thechamfered portion (56) of the present variation are respectively uniformaround the entire periphery (52 a) of the outlet end (52) of thedischarge port (50). The cross sectional shape of the discharge port(50) of the present variation is not limited to an accurate ellipsehaving two focus points, but may be a shape whose periphery is formed bya curve and which looks like an ellipse at a glance.

Sixth Variation of Embodiment

As shown in FIG. 18, the compressor mechanism (30) of the compressor(10) of the present embodiment may be a rotary fluid machine of rollingpiston type, in which the blade (43) is formed independently from thepiston (38). In the compressor mechanism (30) of the present variation,the flat plate-like blade (43) is fitted in a blade groove extending inthe radius direction of the cylinder (32) so as to be capable of movingto and fro, and the bushes (41) are omitted. The blade (43) is pressedagainst the outer circumferential surface (39) of the piston (38) by aspring (44), and the end portion of the blade (43) slides with the outercircumferential surface (39) of the piston (38).

In the compressor mechanism (30) shown in FIG. 18, the cross sectionalshape of the discharge port (50) is a circle. However, the crosssectional shape of the discharge port (50) of the present variation maybe an oblong shown in FIG. 6 or an ellipse shown in FIG. 17.

INDUSTRIAL APPLICABILITY

As described above, the present invention is useful for a compressorhaving a discharge valve.

DESCRIPTION OF REFERENCE CHARACTERS

10 compressor

30 compressor mechanism

36 compression chamber

38 piston (movable side member)

45 fixed site member

50 discharge port

51 inlet end

52 outlet end

56 chamfered portion

60 discharge valve

61 valve body

1. A compressor comprising: a fixed side member forming a compressionchamber; and a movable side member which is rotated and changes a volumeof the compression chamber, the compressor being configured to suck afluid into the compression chamber and to compress the fluid, the fixedside member being provided with a discharge port that penetrates thefixed side member and leads the fluid out of the compression chamber,and a discharge valve that opens/closes the discharge port, thedischarge valve having a valve body which closes the discharge port bycovering an outlet end of the discharge port and opens the dischargeport by being titled from the outlet end of the discharge port, an areaof an inlet end of the discharge port being Ai, a peripheral length ofthe inlet end being Li, and a hydraulic diameter Di of the inlet endbeing defined by Di=4(Ai/Li), a peripheral length of the outlet end ofthe discharge port being Lo, a reference lift amount of the valve bodybeing ho, a cross sectional area Ao of an outlet side flow path formedbetween the outlet end of the discharge port and the valve body beingdefined by Ao=Lo×ho, and a hydraulic diameter Do of the outlet side flowpath being defined by Do=4(Ao/2Lo), and a ratio (Do/Di) of the hydraulicdiameter Do of the outlet side flow path to the hydraulic diameter Di ofthe inlet end of the discharge port being 0.25 or more and 0.5 or less.2. The compressor of claim 1, wherein the ratio (Do/Di) of the hydraulicdiameter Do of the outlet side flow path to the hydraulic diameter Di ofthe inlet end of the discharge port is 0.4 or less.
 3. (canceled)
 4. Thecompressor of claim 1, wherein the fixed side member is provided with achamfered portion along an entire periphery of the outlet end of thedischarge port.
 5. The compressor of claim 6, wherein a height H of achamfered portion in an axial direction of the discharge port and awidth W of the chamfered portion in a direction orthogonal to the axialdirection of the discharge port satisfy a relationship of 0<H/W<0.5. 6.The compressor of claim 1, wherein a cross sectional shape of thedischarge port is oblong or an ellipse
 7. The compressor of claim 2,wherein the fixed side member is provided with a chamfered portion alongan entire periphery of the outlet end of the discharge port.
 8. Thecompressor of claim 2, wherein a cross sectional shape of the dischargeport is oblong or an ellipse.
 9. The compressor of claim 3, wherein across sectional shape of the discharge port is oblong or an ellipse. 10.The compressor of claim 8, wherein a height H of a chamfered portion inan axial direction of the discharge port and a width W of the chamferedportion in a direction orthogonal to the axial direction of thedischarge port satisfy a relationship of 0<H/W<0.5.
 11. The compressorof claim 9, wherein a height H of the chamfered portion in an axialdirection of the discharge port and a width W of the chamfered portionin a direction orthogonal to the axial direction of the discharge portsatisfy a relationship of 0<H/W<0.5.